Mass culture of Undaria gametophyte clones and their use in sporeling culture

Undaria pinnatifida (Harv.) Sur. is one of the three main seaweed species under commercial cultivation in China. In the mid-1990s the annual production was about 20 000 tons dry. The supply of healthy sporelings is key to the success of commercial cultivation of Undaria. Previous studies demonstrated that instead of the zoospore collection method, sporelings can be cultured through the use of gametophyte clones. This paper reports the experimental results on mass culture of clones and sporeling raising in commercial scale. Light had an obvious effect on growth of gametophyte clones. Under an irradiance of 80 μmol m−2 s−1 and favorable temperature of 22–25 °C, mean daily growth rate may reach as high as 37%. Several celled gametophyte fragments were sprayed onto the palm rope frame. Gametogenesis occurred after 4–6 days. Juvenile sporeling growth experiments showed that nitrate and phosphate concentrations of 2.9 10−4 mol l−1 and 1.7 10−5 mol l−1 were sufficient to enable the sporelings to maintain a high daily growth rate. Sporelings can reach a length of 1 cm in a month. Since 1997, extension of the clone technique has been carried out in Shandong Province. Large-scale production of sporelings for commercial cultivation of 14 and 31 hectares in 1997 and 1998 had been conducted successfully.